1. How have advances in technology affected the safety of vehicles?

2. Unit Questions
What forces act on a car and on the body during a car crash?
What are some causes of vehicle crashes?
What are 3 types of collisions that occur during a car crash?
How can vehicles be made safer?
What can you do to be safe in a vehicle?

3. Car Crash Physics
By Lisa Atwell

4. Overview Forces acting on your car and body in a car crash
Physics of moving objects
Newton’s Laws of Motion
3 types of collisions that occur during a car crash
Causes of car crashes
Vehicle safety

5. The Physics of Moving Objects
momentum
Impulse
Velocity
Speed
time
Mass
Acceleration

6. Is how much matter is in something.
MASS
Is how much matter is in something.
The more you stuff in your suitcase,
the more massive it becomes.

7. Is how fast something is traveling.
Speed
Is how fast something is traveling.
Near your school, your mother presses on the gas pedal to make the car go 15 mph (miles per hour)
On Interstate 82, your father presses on the gas pedal to make the car go 70 mph.
Direction is not important !

8. Speed is
distance
time

9. Is how fast something is going and
Velocity
Speed
Is how fast something is going and
in which direction. +
direction

10. Velocity is
distance
direction
in a
time
55 mph south

11. When a car accelerates, it may be speeding up or slowing down.
Acceleration is
Speed
the change in
When a car accelerates, it may be speeding up or slowing down.

12. Remember: Mass is the amount of matter in something.
Speed is how fast something is traveling.
Velocity is how fast something is traveling in a direction.
Acceleration is a change in speed.

13. Experiment #1
Velocity or
Acceleration?

14. Newton’s 2nd Law of Motion
F = ma
Force equals mass times acceleration
Force
is a push or a pull.
This law means that while you are applying a force on an object, it will continue to accelerate or change its velocity. It also states that the greater the force on an object, the greater the acceleration.

15. Do you know the word that describes a
MASS
in motion ?

16. Here is a clue: omentum m
The Starkville Academy running back is running toward the goal.
The Heritage linebacker grabs his legs
one yard from the goal line.
The running back can’t move his legs, but still scores for SA and wins the game!
The announcer says the player’s
omentum m
carried him over the goal line.

17. in motion ! Momentum = mass x velocity momentum MASS is
All objects have mass.
If an object is moving, it has momentum.

18. Momentum and its relationship to mass and speed
Suppose the 150 lb Starkville Academy running back has a speed of 10 mph going east.
Suppose the 100 lb Heritage Academy line backer has a speed of 10 mph going west.
They collide head on at the goal line.
What are the results ?

19. Momentum = mass x velocity
The Starkville Academy player has a mass of 150 lb and is running 10 mph toward the east.
1500 lb mph east
His momentum is
The Heritage Academy player has a mass of 100 lb and is running 10 mph toward the east.
1000 lb mph west
His momentum is
The result is a final momentum of 500 lb mph east (towards the goal line).

20. time time Impulse Force . Impulse Impulse Force . x
the force is applied
A moving car has momentum.
When this car crashes, it’s momentum is changed. .
A change in momentum is called an
Impulse
Impulse
is an applied
Force
time .
over a period of

21. Remember: Mass is how much matter is in something.
Acceleration is how fast you are changing your speed.
Velocity is speed in a direction.
A force is a push or a pull.
Momentum is mass in motion.
Impulse is the force times the time the force is applied.

22. Experiment #2
Egg Toss
Stop that egg!

23. In the car’s collision, the
Force
Determines the amount of damage to the car and the passengers

24. Inertia Newton’s First Law of Motion
Without a push or a pull, an object
at rest remains at rest and an object
in motion remains in motion.

25. Newton’s 3rd Law of Motion
When object 1 pushes on object 2
with a force
object 2 pushes back on object 1
with the same force
but
in the opposite direction.

26. What causes vehicle crashes?
Speeding
Too many lane changes
Following too closely
Running red lights
Distractions
Driving while under the influence

27. Have you ever wondered what happens
inside a car when it crashes?
In each car crash
there are actually three collisions:
The Car's Collision
The Human Collision
The Internal Collision

28. to the car and driver is great.
time
If the
to stop a is
small,
Force
Then the stopping is
LARGE
damage
and the
to the car and driver is great.

29. time to stop a If the LARGE, Force the stopping small and the is is
damage
and the
to car and driver is less.

30. In a Car's Collision During a crash, the car crashes to a stop.
At 30 mph, a car hitting an object that is not moving will crumple in about two feet.
As the car crushes, it absorbs some of the force of the collision and increases the stopping time.

31. time time Force. less car wreck, In a increased is the stopping
More stopping
means
less
car wreck,
In a
increased is
time
the stopping
collapsible
by having a
front end and bumper on the car.

32. The Human Collision
At the moment of impact, passengers in the automobile are still traveling at the vehicle’s original velocity.
When the car comes to a complete stop the passengers continue to be hurled forward until they come in contact with some part of the automobile (the steering wheel, the dashboard, the front window or back of the front seat).

33. Humans in a crash can also cause serious injuries to other humans when they collide with each other.
People in the front seat of a car are often hit by rear-seat passengers as they fly forward with incredible force.

34. The Internal Collision
In a crash, even after a human body comes to a complete stop, its internal organs are still moving.
Suddenly, these internal organs slam into other organs or the skeletal system.
This "internal collision" is what often causes serious injury or death.

35. What happens when two objects collide?
Influences:
Mass
Velocity
Time
Momentum
Impulse
The impulse experienced by the car equals a change in momentum.
As car designers, we only have control over mass and time.

36. What Helps Drivers and Passengers Survive Collisions?
Air Bags
Seatbelts
Bumpers

37. Seatbelts
Purpose is to restrain passengers from tossing back and forth after a collision
Lap belt protects the pelvis and the shoulder belt protects the rib cage
Have ability to extend and retract, but in a collision the belts will suddenly tighten up and hold passengers in place

38. Air Bags Purpose is to slow down passengers speed after a crash
A soft pillow to land against in a crash
Works within a fraction of a second

39. Sometimes an air bag or seatbelt is used to stop the passenger
No airbag
No seatbelt
No seatbelt
with baby
Hit from
behind
stop the passenger
Seat belts

40. Bumpers
The bumper’s purpose is to absorb crash energy without significant damage to the bumper itself and no damage to the vehicle’s rear or front end.
Low speed crashes mostly occur in urban traffic.
Less damage is done in a collision when 2 vehicles are lined up bumper to bumper.
Bumpers can protect other components of a vehicle.

41. But as the driver, please remember,
Speed
does kill.

42. Total Stopping Distance (ft) Breaking Distance (ft)
Distance it takes to safely stop a car
Total Stopping Distance (ft)
Speed
(mph)
Reaction Time (ft)
Breaking Distance (ft) 10 11 6 17 20 22 24 46 50
60.5
181.5
242 65
253.5
325 70 77
294
371
Longer than a
football field

43. How many times have you heard people say…
“I don’t need to buckle up.”
“I am just going around the block.”
“I was just going 30 mph.”
While it is true that slower speeds reduce the risk,
don’t forget that seat belt!
11 percent of all fatal crashes occurred when the car was going 30 mph or less.

44. Think of the following scenarios, when you make that choice to use your seat belt:
At 3 mph
Imagine that you are hit head-on by a football tackle running 3 mph. He knocks you flat and your head hits the turf. You wake up in the hospital with a serious concussion and a sprained neck.
At 15 mph
Imagine shoving your face into the windshield or your chest into the steering wheel at that speed, with no helmet, no pads, and no chance to brace yourself

45. Would you jump? At 35 mph At 40 mph
You are driving at 35 mph when a deer darts in front of your car. You brake quickly, miss the deer and keep your car on the road. Shaken up, you pull over. An officer stops to offer assistance and then issues a citation for not buckling up. "Next time, you might not be so lucky,” he says.
At 40 mph
Suppose you stand on top of a five story building and fall off head first.
This represents 40 mph.
Would you jump?

46. Remember,
More stopping time,
means
less force!!

47. Experiments Bumper Design Automotive Design Challenge
Engineering Challenge

48. Questions
What are the three types of collisions that occur during a car crash?
What are some causes of car crashes?
How can you remain safe in a car?

49. Resources
CAVS Outreach Program, Cuicchi, P., & Cuicchi, R. (n.d.). Mission eggcellence challenge [Brochure]. (Available from Center for Advanced Vehicular Systems, Mississippi State University)
Henderson, T. (1996). Lesson 4: Newton’s third law of motion. In The physics classroom tutorial. Retrieved March 2, 2008, from Glenbrook South High School Web site:
Henderson, T. (1996). Speed and velocity. In The physics classroom tutorial. Retrieved March 2, 2008, from Glenbrook South High School Web site:
Wirt, S. (1999). The physics zone: Forces, accelerations, and car accidents. Retrieved
March 2, 2008, from Oswego City School District Web site:
Zobel, E. (1997). Newton’s second law of motion. Retrieved March 2, 2008, from